The biggest giveaway sits behind the lower grille. Our spies call it an oil cooler but it might be an intercooler. That's speculation – the detail on these few images isn't enough to draw a firm conclusion on what's hiding behind the ST's new face. The camouflage is heavy, but the upper grille looks bigger on the ST, like the difference between the Focus and the Focus ST. And the spoiler on this car looks bigger than the Fiesta we saw a few weeks back, but we don't have the best angle for making a comparison.
Usually, wheels are a big giveaway about a car's true nature, but not in this case. Both this ST and the standard car we saw a couple weeks ago wear current Fiesta ST's wheels – five spokes on the normal car and multi-spokes for the ST. Ford could have been trying to hide larger brakes with the black multi-spokes, but the front rotors and calipers don't look bigger. More than likely, Ford may have just had a set of wheels laying around, and threw them on the ST prototype. That said, the ride height may be just a smidge lower on this car.
The Fiesta, like the Fiesta ST, is expected to be a 2018 model-year vehicle. That would imply a debut late next year, perhaps at the Frankfurt Motor Show.